I. Field of the Invention
The present invention relates generally to the field of hydraulic cylinders and more particularly to a self-locking hydraulic cylinder apparatus.
II. Description of the Related Art
Currently, if a load is to be lifted and secured by a hydraulic cylinder, there must exist an external locking mechanism or an internal/external hydraulic valve to hold the load in place. Mechanical locks require additional components and usually only lock the load in distinct increments. Hydraulic valves drift down over a period of time due to possible seal or spool leakage. Furthermore, in case of hydraulic fluid pressure failure, there must be a mechanism to prevent the lowering of a load.
FIG. 3 illustrates a car trailer 600 having a prior art cylinder assembly. Two hydraulic cylinders 605, 610 can raise or lower a car level 615. This double cylinder configuration can be used to prevent the level 615 from lowering as it might if just one cylinder were used to raise it.
FIG. 4A illustrates a car trailer having a prior art hydraulic cylinder assembly 705. A hydraulic cylinder 710 can be pressurized with hydraulic fluid to extend and retract levels of the car trailer 700. An additional mechanical cylinder 715 is used to set the levels in place after the hydraulic cylinder 710 raises or lowers the levels. A mechanical device 720 is used on the mechanical cylinder as a setting device. A set screw 725 is used to tighten a cuff 730 around a rod 735 to keep the rod 735 from retracting into a housing 740. Alternatively, the device 720 is a spring loaded set pin (not shown) that inserts into a hole on the rod 735. Having this mechanical setting keeps the levels in place if the hydraulic cylinder 710 begins to retract for any reason such as fluid leakage.
FIG. 4B illustrates a car trailer 750 having a prior art hydraulic cylinder assembly 755. A hydraulic cylinder 760 can be pressurized with hydraulic fluid to extend and retract levels of the car trailer 750. An additional mechanical cylinder 765 is used to set the levels in place after the hydraulic cylinder 760 raises or lowers the levels. The mechanical cylinder 765 has a series of pinholes 770 that are adapted to receive a set pin (not shown). Once the hydraulic cylinder raises or lowers the levels to the desired position, the set pin can be placed in one of the holes 770 to keep the hydraulic cylinder from retracting.
Each of these prior art assemblies requires an external mechanical mechanism that typically has to be set by a human in order to set the hydraulic cylinder in place.
In accordance with the present invention and the contemplated problems which have and continue to exist in this field, the invention features a hydraulic locking cylinder having an integral self-contained locking mechanism. The locking cylinder holds a load imposed on the cylinder without any external mechanism and without additional hydraulic valves or interaction. It holds the load indefinitely without drifting down. In particular embodiments, the cylinder is hydraulically operated and forces hydraulic fluid in and out of three separate ports as selected and needed. In another embodiment, the cylinder is hydraulically operated and forces hydraulic fluid in and out of two ports using a shuttle valve to direct and redirect the fluid. The cylinder uses a continuous screw that extends the length of the hydraulic cylinder and is turned by the input of hydraulic fluid in the various hydraulic ports. As the cylinder extends and retracts, the screw turns. A self locking feature includes an internal locking rod that engages a notch on the head of the screw. The engagement and disengagement of the screw depends on the force caused by the input of hydraulic fluid into the ports as well as the force of the load, typically a gravitational force.
One advantage of the invention is that the cylinder is self-contained and needs no additional external mechanisms to lock.
Another advantage is that in the event of hydraulic fluid pressure failure, the cylinder locks at substantially the same point at which the pressure is removed.
In one aspect, the invention features a locking cylinder, including a screw shaft having a head and a threaded rod, wherein the head has a radius larger than the rod, the head having a top surface, a nut in threaded engagement with the threaded rod, a piston, having a hollow center, connected to the nut, the piston being adapted to receive the threaded rod when the nut screws onto the screw shaft, a substantially cylindrical rod, with one end connected to the piston, wherein the screw shaft, the nut, the piston, and the rod share a longitudinal axis, wherein the top surface of the head is substantially perpendicular to the longitudinal axis, a generally cylindrical housing surrounding the screw shaft, the nut, the piston and the rod, wherein the rod extends out of one end the housing along the longitudinal axis, wherein the longitudinal axis of the housing is the same as the longitudinal axis.
In an implementation, one end of the housing has an inner wall with a radius substantially the same as a radius of the rod, and wherein an elongated portion of the center of the housing has an inner wall with a radius substantially the same as a radius of the piston, and wherein the other end of the housing has an inner wall with a radius substantially the same as the head of the screw shaft.
In another implementation, the perimeter of the head of the screw shaft is in contact with the inner wall of the housing having the radius the same as the head, and wherein the perimeter of the piston is in contact with the inner wall of the housing having the same radius as the piston, and wherein the perimeter of the rod is in contact with the inner wall of the housing having the same radius as the rod.
In still another implementation, the cylinder includes a first seal in the inner wall of the housing having the same radius as the head, the seal running along the perimeter of the head, and in contact with the head, a second seal running along the perimeter of the piston and in contact with the inner wall having the same radius as the piston and a third seal in the inner wall of the housing having the same radius as the rod, the third seal running along the perimeter of the rod, and in contact with the rod.
In yet another implementation, the end of the housing opposite the end of the housing having the rod extending from it, has a closure, the closure having an inner wall internal to the housing, and substantially perpendicular to the longitudinal axis and the inner wall of the closure faces the top surface of the head.
In another implementation, the top surface of the head further comprises a notch at a location on the surface less than the radius of the head.
In another implementation, the cylinder further includes a locking rod substantially connected to the inner wall of the closure and perpendicular to the inner wall of the closure, the locking rod adapted to engage the notch.
In another aspect, the invention features a hydraulic cylinder including a substantially cylindrical housing having a longitudinal axis and a first and second end, the first end having a inner face and an outer face, the inner and outer faces being substantially perpendicular to the longitudinal axis, and the second end having an opening defined by a plane substantially perpendicular to the longitudinal axis, a screw shaft having a substantially cylindrical head portion having a first radius, a substantially cylindrical threaded portion having a second radius, the threaded portion being substantially perpendicular with a geometric cross section of the head portion, wherein the head portion and the threaded portion have a longitudinal axis common with the longitudinal axis of the housing, and wherein the geometric cross section is substantially perpendicular with the common longitudinal axes and a rod having a substantially cylindrical ball nut having a first and second open end, and an inner and outer surface, the inner surface being threaded and adapted to engage the threaded portion of the screw shaft, a substantially cylindrical piston having a first end and a second end, the first end being connected to one of the ball nut ends, an end portion connected to the second end of the piston, wherein the end portion intersects the opening defined by the plane on the second end of the housing, wherein the ball nut, the piston and the end portion have a longitudinal axis common with the longitudinal axis of the housing.
In an implementation, the cylinder includes a locking rod substantially perpendicular to the inner face of the first end of the housing.
In another implementation the cylinder includes hydraulic fluid inputs.
In still another aspect, the invention features a vehicle transporter, including a plurality of vehicle platforms, each having a plurality of hydraulic cylinders to lift and position the platforms, the cylinders including a substantially cylindrical housing having a longitudinal axis and a first and second end, the first end having a inner face and an outer face, the inner and outer faces being substantially perpendicular to the longitudinal axis, and the second end having an opening defined by a plane substantially perpendicular to the longitudinal axis, a screw shaft having a substantially cylindrical head portion having a first radius, a substantially cylindrical threaded portion having a second radius, the threaded portion being substantially perpendicular with a geometric cross section of the head portion, wherein the head portion and the threaded portion have a longitudinal axis common with the longitudinal axis of the housing, and wherein the geometric cross section is substantially perpendicular with the common longitudinal axes, a rod having a substantially cylindrical ball nut having a first and second open end, and an inner and outer surface, the inner surface being threaded and adapted to engage the threaded portion of the screw shaft, a substantially cylindrical piston having a first end and a second end, the first end being connected to one of the ball nut ends, an end portion connected to the second end of the piston, wherein the end portion intersects the opening defined by the plane on the second end of the housing, wherein the ball nut, the piston and the end portion have a longitudinal axis common with the longitudinal axis of the housing and a locking rod substantially perpendicular to the inner face of the first end of the housing.
In still another aspect, the invention features a locking cylinder, including a screw shaft having a head and a threaded rod, wherein the head has a radius larger than the rod, the head having a circumferential surface, a piston having a hollow center and internal threads, the piston adapted to receive the threaded rod when the internal threads screw onto the screw shaft, a substantially cylindrical rod, with one end connected to the piston, wherein the screw shaft, the piston, and the rod share a longitudinal axis, a generally cylindrical housing surrounding the screw shaft, the piston and the rod, wherein the rod extends out of one end the housing along the longitudinal axis, wherein the longitudinal axis of the housing is the same as the longitudinal axis.
In an implementation, the cylinder further includes a casing connected to the housing and enclosing the head of the screw shaft, the casing including a plunger enclosed within a chamber within the casing and oriented substantially perpendicular to the longitudinal axis and to a portion of the circumferential surface, a first end of the plunger in proximity of the circumferential surface and a spring coupled to a second end of the plunger.
In still another implementation, the circumferential surface includes at least one engagement notch oriented radially outward from the circumferential surface, wherein the notch is adapted to receive the first end of the plunger.
In another implementation, the cylinder includes hydraulic fluid inputs.
In yet another implementation, the casing further includes a shuttle valve assembly having hydraulic fluid inputs, the assembly adapted to route hydraulic fluid to different sections of the housing and to the portion of the casing having the plunger.
In still another implementation, the casing further includes a hydraulic fluid input adapted to route fluid to the portion of the casing having the plunger.
In yet another aspect, the invention features a vehicle transporter, comprising a plurality of vehicle platforms, each having a plurality of hydraulic cylinders to lift and position the platforms, the cylinders including a screw shaft having a head and a threaded rod, wherein the head has a radius larger than the rod, the head having a circumferential surface, a piston, having a hollow center and internal threads, the piston being adapted to receive the threaded rod when the internal threads screw onto the screw shaft, a substantially cylindrical rod, with one end connected to the piston, wherein the screw shaft, the piston, and the rod share a longitudinal axis, a generally cylindrical housing surrounding the screw shaft, the piston and the rod, wherein the rod extends out of one end the housing along the longitudinal axis, wherein the longitudinal axis of the housing is the same as the longitudinal axis and a casing connected to the housing and enclosing the head of the screw shaft, the casing including a plunger enclosed within a chamber within the casing and oriented substantially perpendicular to the longitudinal axis and to a portion of the circumferential surface, a first end of the plunger in proximity of the circumferential surface and a spring coupled to a second end of the plunger, wherein the circumferential surface includes at least one engagement notch oriented radially outward from the circumferential surface, wherein the notch is adapted to receive the first end of the plunger.
In another aspect, the invention features hydraulic locking cylinder, including a housing enclosing a rod and piston assembly in threaded engagement with a screw shaft and means for locking the screw shaft thereby preventing rotation of the screw shaft.
Other objects, advantages and capabilities of the invention will become apparent from the following description taken in conjunction with the accompanying drawings showing the preferred embodiment of the invention.